The Frontal Aslant Tract and Supplementary Motor Area Syndrome: Moving towards a Connectomic Initiation Axis

Abstract

Connectomics is the use of big data to map the brain's neural infrastructure; employing such technology to improve surgical planning may improve neuro-oncological outcomes. Supplementary motor area (SMA) syndrome is a well-known complication of medial frontal lobe surgery. The 'localizationist' view posits that damage to the posteromedial bank of the superior frontal gyrus (SFG) is the basis of SMA syndrome. However, surgical experience within the frontal lobe suggests that this is not entirely true. In a study on n = 45 patients undergoing frontal lobe glioma surgery, we sought to determine if a 'connectomic' or network-based approach can decrease the likelihood of SMA syndrome. The control group (n = 23) underwent surgery avoiding the posterior bank of the SFG while the treatment group (n = 22) underwent mapping of the SMA network and Frontal Aslant Tract (FAT) using network analysis and DTI tractography. Patient outcomes were assessed post operatively and in subsequent follow-ups. Fewer patients (8.3%) in the treatment group experienced transient SMA syndrome compared to the control group (47%) (p = 0.003). There was no statistically significant difference found between the occurrence of permanent SMA syndrome between control and treatment groups. We demonstrate how utilizing tractography and a network-based approach decreases the likelihood of transient SMA syndrome during medial frontal glioma surgery. We found that not transecting the FAT and the SMA system improved outcomes which may be important for functional outcomes and patient quality of life.

Keywords: SMA syndrome; connectomics; frontal aslant tract; glioma surgery; neuro-oncology; neurosurgery; parcellation; tractography.

Figure 1

The FAT was identified by placing a ROI seed, seen as a white square, near the cranio-caudal fibres which terminate anterior to the arcuate fasciculus frontal projections at the level of the inferior frontal gyrus (IFG).

Figure 2

These figures demonstrate the relative position of the major white matter tracts relevant to SMA. The corticospinal tract is in blue, the FAT in red, the arcuate fasciculus is in orange and the cingulum fibres are in mauve. (a) Demonstrates the tumour pushing the FAT fibres behind towards the primary motor cortex; (b) Demonstrates the tumour between the FAT and the primary cortex, pushing the FAT anteriorly.